1. Field of the Invention
This invention relates to a blade, particularly to a cleaning blade for cleaning and removing by scraping the toner remaining on the surface of an electrophotographic photosensitive member surface.
2. Related Background Art
A blade article is molded in the shape of a plate comprising a rubber elastomer and has been used, for example, for cleaning and removing foreign matter attached on a flat surface by moving physically in contact with the surface.
On the other hand, in an electrophotographic photosensitive member assembled in an electrophotographic copying machine or a laser beam printer, the cleaning characteristics of the surface are very important, and as one cleaning method, the residual toner on the photosensitive member is cleaned and removed by contacting a blade comprising a polymeric elastomer such as urethane rubber, chloroprene rubber, ethylene-propylene diene rubber, nitrile rubber, etc. with the electrophotographic photosensitive member.
When residual toner on the photosensitive member is to be cleaned with a rubber blade, rubber generally has a high in coefficient of friction and yet also excessive in abrasion, and therefore when used forcibly, it will be subject to rapid and nonuniform abrasion, causing defective cleaning to occur or, and in an extreme case, will damage the photosensitive member surface.
In order to improve durability, lubricity, and the cleaning characteristics by improvement of such points, there have been made contrivances such as incorporation of a compound with low surface energy and having lubricity, such as silicone oil, etc. into the polymeric elastomer.
For example, as disclosed in Japanese Patent Laid-open Application No. 57-37385, a cleaning blade is formed by the addition of a silicone oil before crosslinking of a urethane rubber, or as disclosed in Japanese Patent Laid-open Application No. 59-15967, with the mold surface being coated with a silicone oil, a urethane is injected into the mold to carry out the reaction, thereby forming a cleaning blade. Also, as disclosed in Japanese Patent Laid-open Application No. 57-128376, Japanese Patent Laid-open Application No. 57-201276, Japanese Patent Laid-open Application No. 57-201277, a polyester is mixed and reacted with an organic diisocyanate to form a prepolymer, and the prepolymer formed is mixed with a low surface energy compound such as silicone oil, polysiloxane oil or modified polysiloxane oil, etc., followed by heating curing to mold a cleaning blade. Further, as disclosed in Japanese Patent Laid-open Application No. 59-5259, the prepolymer obtained by reacting silicone oil with an isocyanate is coated on a cleaning blade comprising a urethane, followed by heating to carry out the reaction, thereby molding a blade.
However, when cleaning is performed with a blade comprising a polymeric elastomer containing a low surface energy compound molded according to the method of the prior art, due to scraping between the blade and the photosensitive surface with progress of repeated successive copying of electrophotographic process, the blade edge portion will be nonuniformly abraded. For this reason, the cleaning effect of residual toner will be lowered to a great extent, whereby there has been involved the problem that no sufficient durability can be obtained.
Also, as the copying machine or laser beam printer has been recently made higher in speed recently, a photosensitive member of high durability and long life has been developed, which can stand even 100,000 sheets of successive copying. Such a photosensitive member is constituted of an inorganic material such as amorphous silicon, and its surface hardness is very hard (in the case of amorphous silicon drum, Vickers hardness of 1500 to 2000 Kg/cm.sup.2). When a blade of the prior art is applied to such a photosensitive member of and long durability, high life, there is the problem that durability is insufficient, and the blade must be exchanged frequently, and it has been desired to have a blade of high durability which can correspond to such a photosensitive member of high durability and long life under the present situation.